Radwanska, the top seed and world number four, quickly disposed of former Auckland champion Greta Arn 6-2, 6-2.
Top seed Roberta Vinci was ousted from the $220,000 WTA Monterrey Open on Wednesday, with Russian Nina Bratchikova upsetting the Italian 7-5, 7-5 to reach the quarter-finals.
Serena Williams was so dominant in her 6-1, 6-1 third-round win over Greta Arn at the Australian Open that there's probably only one shot she'll remember more than most.